1. Field of the Invention
The present general inventive concept relates to a selective surface treatment method using a block copolymer, a black matrix and a method of manufacturing the same, and a nozzle plate and a method of manufacturing the same.
2. Description of the Related Art
Liquid crystal display devices include a color filter that allows light modulated by a liquid crystal layer to pass therethrough in order to form an image with a required color. The color filter is manufactured by forming a black matrix on a transparent substrate and filling ink of a predetermined color such as red, green, or blue in all pixels defined by the black matrix. When the black matrix includes both ink-philic upper and side surfaces, ink injected in the pixels may flow over an upper surface of the black matrix, thereby causing ink color mixture. Alternatively, when the black matrix includes both ink-phobic upper and side surfaces, the ink color mixture between the pixels can be prevented. However, the side surfaces of the black matrix do not have sufficient wetting for ink, and ink cannot be applied to a uniform thickness in each pixel.
Therefore, in order to form ink to a uniform thickness in the pixels and also prevent the ink color mixture between the pixels, the black matrix may include an ink-phobic upper surface and an ink-philic side surface. As one surface treatment method for this purpose, an ink-phobic coating film may be selectively formed on only an upper surface of an ink-philic black matrix. However, if the ink-phobic coating film is formed too thick, development thereof is difficult. Also, if the ink-phobic coating film is formed too thin, the ink-phobic coating film may be easily separated from the black matrix due to weak adhesion therebetween. This is because the black matrix and the ink-phobic coating film are formed of materials with properties different from each other. Therefore, an ink-phobic material having very good adhesion with the ink-philic black matrix is required.
Inkjet heads are devices used to form color images on printing mediums by discharging ink droplets onto a desired region of a printing medium through nozzles of a nozzle plate. Inkjet heads can be classified into two types depending on the ink ejecting mechanism: thermal inkjet heads and piezoelectric inkjet heads. The thermal inkjet head ejects ink based on an expansion of the bubbles generated by heat, and the piezoelectric inkjet head ejects ink using a pressure generated by a deformation of a piezoelectric material.
In the inkjet head, a surface treatment of the nozzle plate directly affects the ink ejection performance, for example, directivity and ejection speed of ink droplets ejected through nozzles, or the like. That is, in order to improve the ink ejection performance, inner walls of the nozzles should be ink-philic, and a surface of the nozzle plate outside the nozzles should be ink-phobic. In detail, when the nozzles have ink-philic inner walls, a contact angle for ink decreases and a capillary force increases, and thus the refill time of ink can be reduced, thereby increasing the ejection frequency of the nozzles. Also, when the nozzle plate outside the nozzles has an ink-phobic surface, ink wetting can be prevented on the surface of the nozzle plate to improve the directivity of ink. Accordingly, the nozzle plate may include an ink-philic surface and an ink-phobic coating film may be selectively formed on only a surface of the nozzle plate outside the nozzles. Here, the ink-phobic coating film should have a constant contact angle for ink even after a sequence of maintenance processes of the inkjet head. In detail, the ink-phobic coating film should have excellent adhesion with the surface of the nozzle plate in order to improve the durability thereof. For this purpose, an ink-phobic material having very good adhesion with the ink-philic surface of the nozzle plate is required.